1.1 Technical Field
This invention pertains to a method and device for indicating failures within a radon mitigation system. The method involves installation and use of a device to detect malfunctions in a radon mitigation system and provide notice of such a malfunction.
1.2 Background Art
The presence of radon gas in occupied buildings may contribute to incidence of lung cancer. Because of the possible detrimental effects of radon, the United States Environmental Protection Agency (EPA) recommends that radon levels in occupied structures be maintained at less than 4 PicoCuries per liter (4 pCi/l). Radon is a naturally occurring gas, which ma infiltrate buildings in concentrations higher than the maximum EPA recommended guidelines. In these situations, a variety of mechanical systems may be used to reduce radon concentrations.
For example, radon may be removed from a building by creating a mechanically induced vacuum beneath the building, into which the radon may be collected. Alternatively, ventilation in the structure may be increased to remove radon from the structure. Both of these strategies rely on the installation and use of electric fans.
A malfunction in a radon removal system, such as a pluggage in the associated piping system due to debris or ice, or a breach of the piping system, can result in the system not performing as originally designed. Since radon is a colorless and odorless gas, the building owner may not be aware of the decrease in radon removal efficiency due to these conditions, unless some type of failure indication is provided. Furthermore, failures of this type may cause other detrimental conditions within the structure if left unnoticed which can cause significant hazards and operating costs. A device is needed which can detect slight to large increases and decreases in air volume of the fan used for radon mitigation.
The EPA has recommended that each radon removal system include a method of detecting a failure in the mitigation system. See "Radon Contractor Proficiency Program Interim Radon Mitigation Standards," Dec. 15, 1991. Methodology presently utilized within the radon industry to satisfy this recommendation utilizes a pressure indicator that does not sense air flow and therefore does not provide sufficient information to easily detect most system failures. Furthermore, pressure indicators are invasive to the system and have the potential for in-building leaks of radon a well as accumulation of moisture which provides false readings. A system is needed which is totally electric and outside of the air stream and therefore not subject to these potential defects.
Air quality control systems including mechanisms for detecting system failures are known in the prior art. For example, U.S. Pat. No. 4,352,349 to Yoho describes a control circuit for air conditioning systems. The Yoho circuit includes an electrical sensor and temperature sensor for determining whether an exhaust fan is properly operating over a grill in a restaurant. If the exhaust fan is not functioning properly, the circuit is designed to turn off the grill.
Other air purification systems may include sensors to determine when air quality warrants activation of the purification process. For example, the air make-up unit described in U.S. Pat. No. 4,362,922 to Anderson draws outside air into a building, by means of an electric blower. The blower may be activated by a pressure sensor when negative pressure develops within the building.
Similarly, U.S. Pat. No. 4,726,824 to Staten teaches an air purification system to remove pollutants from indoor air. The system includes sensors to determine the presence of such chemicals as ozone and carbon monoxide, which trigger the operation of the air purification mechanism.
Temperature sensors are used in the control system described in U.S. Pat. No. 4,189,094 to Robinson. That system is designed to ventilate indoor swimming pools, rather than air.
While each of these mechanisms known in the prior art is useful for its intended purpose, no mechanism is known which may be easily installed to monitor the efficacy of a radon mitigation system. There exists a need for a mechanism which can be simply installed, which will monitor the effectiveness of a radon mitigation system, and provide information needed to insure that the system is properly functioning.
2. Disclosure of the Invention
2.1 Summary of the Invention
An object of this invention is to provide a method of detecting air flow in a radon mitigation system to provide an easy to read indication of system performance.
Another object of this invention is to provide a device for monitoring a radon mitigation system, which can be easily installed without requiring the assistance of an electrician.
The device used in this method of detecting and eliminating problems in radon mitigation systems comprises a control unit and a fan voltage booster. The control unit has at least two primary elements: a 120 volt to 24 volt reduction transformer, and a performance indicator. The fan voltage booster is a transformer matching the reduction transformer, which increases voltage from 24 volts to 120 volts, to power a fan in the mitigation system. The fan powered in this manner will typically be a commercially available turbo-blower which is commonly used in radon reduction systems. The fan and fan voltage booster can be packaged as an integral unit.
The performance indicator comprises a 0 to 5 amp ammeter mounted in a panel with a visible face or other mechanism for registering current measurements. The ammeter is connected to the fan in such a way that the ammeter measures the amount of current utilized by the fan.
Many radon mitigation systems depend on specific fan induced air flows for effectiveness. A decrease in air flow may result in a decrease in the efficiency of radon removal. Similarly, if too much air is made available to the system, as would result if air duct or pipe to the fan is broken, the resulting increase in available air would reduce radon removal efficiency. Such an increase in air could also adversely affect the building environment, resulting in increased energy costs and potential combustion appliance backdrafting. Because the fan increases its current draw with increases in air flow, measuring the current draw of the fan also serves as an indicator of the air flow through the fan.
The face of the ammeter may be advantageously calibrated so that the meter indicates that the radon mitigation system is functioning properly whenever the ammeter senses appropriate current draw by the fan. Thus, a section of the face of the ammeter corresponding to the position of the ammeter needle when proper current draw is sensed, can be marked in green or otherwise designated. In this manner, the designated area of the ammeter face becomes a proper conditions indicator, since the radon mitigation system should be functioning properly when the needle of the ammeter is in that region.
Similarly, one or more portions of the ammeter face may be marked in red, or otherwise designated, to indicate that a failure in the radon mitigation system has occurred, whenever the ammeter needle resides in one of those portions. So designated portions of the ammeter face may then be regarded as an improper conditions indicator. As will be apparent, many different types of improper conditions indicators may be utilized. For example, an audible alarm may be connected to the ammeter in such a way that the alarm rounds whenever the ammeter detects fan current draw which is less than or greater than that which is desirable for the system.
The amount of air which needs to be handled by a radon mitigation system is specific to each particular building, and will vary from installation to installation. To compensate for this variation, the ammeter may advantageously include a bias adjustment which allows the installer to set the location of the needle indicator to the "green" or proper conditions indicator area after the system has been fully installed and tested for effectiveness. Consequently, a deviation in the needle position indicates a deviation in the radon system characteristics from when it was originally installed. A shield may be provided for the bias adjustment to prevent accidental adjustment of the bias by building occupants.
The ammeter is directly wired into the circuit of the power supply to the radon fan. The power supply may be standard 120 volt line power, or may be reduced to 24 volts via a power transformer. The latter application has the added advantage that the power output to the fan can be supplied via inexpensive and safer low voltage wiring. This wiring is typically two conductor 16 or 18 gauge jacketed cable which can be routed to a remote location of the radon fan up to 50 feet away. This aspect allows for the fan to be located outside of the living envelope of the building as required by the EPA Mitigation Standards, Dec. 15, 1991, while the ammeter and power supply can be conveniently mounted in a frequently occupied portion of the building for occupant viewing. Furthermore, the low voltage aspect of the power supply to the fan allows for easy installation of the wiring similar to that which would be needed for routing security systems and audio speaker wiring. To allow for proper operation of the radon fan, a matching voltage boosting transformer is connected to the fan to allow for normal, 120 volt operation of the fan. The simplicity of the device should allow for the installation by contractor or building owner, in most electrical code jurisdictional areas, without the assistance of a licensed electrician.
As will be evident, the radon mitigation system control device of the instant invention will also be useful in any situation in which the speed of a fan should be monitored and controlled.
The novel features that ar considered characteristic of the invention are set forth with particularity in the claims. The invention itself, both as to its construction and its method of operation, together with additional objects and advantages thereof, will best be understood from the description of specific embodiments which follows, when read in conjunction with the accompanying drawings.